By Leo Notenboom
If I empty the contents of a file and then save it, is the data really deleted?
You’ve recently spent some time on deleting files. I understand that just hitting Shift+Delete doesn’t rid the hard disk of the file, but I’ve long wondered about some other things: Suppose I have an Excel or Word file that contains personal info (say a list of passwords or other sensitive information) and I decide that’s not such a good idea. If I delete all of the information, then save the file, is that information gone forever? Likewise, suppose this file is called “password.xls,” and I create a new (even blank) spreadsheet, save it as the same file (password.xls), and click ‘Yes’ to “Replace existing file?” Have I successfully hidden those passwords (or whatever) forever? Are they off my disk now? Any chance that life could be this simple?
Let me put it this way: when it comes to computers, life is rarely simple.
This situation is no exception.
The short answer to your question is of course not – the data might still be recoverable.
The longer answer is all about why.
Overwritten files aren’t overwritten
The assumption in your question is that when you update a file with new data, or even removing everything within the file, the new file will be written into the exact same place on the hard disk as the original.
That’s a bad assumption. In fact, it’s not really even what you want the programs to do.
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This post is excerpted with Leo’s permission from his blog.